ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The sequence of atrioventricular activation was studied in two human subjects with type B Wolff-Parkinson-White syndrome (WPW) and in a dog with spontaneous type A WPW. In all three subjects a focal spot of pre-excitation was demonstrated at the A-V margin of the right ventricle (RV). In the two human subjects with type B WPW, the area of pre-excitation was located on the anterior aspect of the RV and in the dog with type A the pre-excited area was located on the posterior aspect of the RV. A probable Kent bundle electrogram was recorded from the A-V margin in one of the human patients. Serial sections (7 &mgr;) of a block taken from the region of pre-excitation in the dog revealed an anomalous A-V communication (Kent bundle). Propagation velocity across this pathway was estimated to be 0.3 mm/msec. Electrophysiologic data recorded from one of the human subjects at the onset and during an episode of supraventricular tachycardia demonstrated an atrioventricular-atrial sequence of excitation. The mechanism of initiation of the tachycardia was a ventriculo-atrial echo following a premature atrial contraction blocked in the anomalous pathway. Surgical separation of right atrium and RV at the site of pre-excitation normalized the activation and ECG and abolished the tachycardia in both patients.Ventricular fibrillation occurred repeatedly in the dog as a direct result of the rapid ventricular rate permitted by the Kent bundle subsequent to induced atrial fibrillation. Correlation of the activation sequence with the body surface potentials suggests an updated conceptual model for electrocardiographic typing of WPW. In a third patient, who demonstrated an atypical form of WPW, the region of pre-excitation could not be precisely defined and interruption of an accessory pathway was unsuccessful.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The catheter technic for recording the electrical activity of the specialized conducting system in the human heart showed in two patients studied that ventricular pre-excitation was apparently due to a bypass of the His bundle. Intermediate forms of WPW complexes appeared to be combination beats resulting from the activation of the ventricles through impulses traversing both the His bundle and accessory communications. Preferential iatrogenic activation of an intra-atrial (and perhaps even of an atrioventricular) tract appeared to occur in one of the patients. The patients with the WPW (pre-excitation) syndrome and long histories of paroxysmal arrhythmias were successfully treated with a combination of oral propranolol and implanted (transvenous) demand pacemaker.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Function of potential bypass tracts for the atrioventricular conduction was examined in isolated rabbit hearts using microelectrodes, a suction electrode, and bipolar electrocardiographic leads. After the normal A-V conduction was blocked by acetylcholine, conduction to the ventricle occurred with a much shorter A-V conduction time and without significant QRS change, when a point at the root of the inferior vena cava was stimulated. By analyzing the site of delay, this route was presumed to go from the right atrium to the lower portion of the His bundle bypassing the A-V node. When a point inferior to this point was stimulated, marked shortening of conduction time and marked QRS change occurred. This second tract seemed to exist between the right atrium and ventricle bypassing the specialized system. The third tract was found when an anterior point on the right atrium was stimulated. The conduction was markedly prolonged without changing the QRS. This route seemed to enter some point of the A-V node, inducing a detour within the node.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Ventriculo-atrial conduction and the reentry phenomenon was studied during right ventricular and bundle of His pacing in the intact dog heart. Bipolar electrogram recordings were obtained from the sinus node, Bachman's bundle, the right and left atria, the bundle of His, and the ventricle. Retrograde conduction resulted in a specific change in the sequence of atrial activation. The recording of both antegrade and retrograde His deflections provided a more accurate means of comparing A-V and V-A conduction times. In all experiments retrograde conduction time exceeded antegrade conduction time. The A-V nodal region was found to be the zone of retrograde conduction delay and block. Increasing the driving rate of the heart, vagal stimulation, and isoproterenol, affected V-A conduction similar to the way in which these maneuvers affect A-V conduction. Reentry (ventricular echoes) commonly occurred when right ventricular or bundle of His pacing resulted in the reverse Wenckebach phenomenon.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Twenty-one patients with complete heart block (CHB) were studied by recording His bundle (BH) electrograms. The site of block was localized proximal or distal to the site at which the BH electrogram was recorded. Eighteen patients had block distal to the recorded BH deflection. One of these 18 patients had a narrow QRS complex indicating block within the His bundle; the other 17 had wide QRS complexes probably due to bilateral bundle-branch block. The three patients with block proximal to the His bundle are examples of A-V nodal block or block in the uppermost portion of the BH. Two of these three had normal QRS complexes; the third with a left bundle-branch block pattern demonstrated that during CHB the ECG criteria for the localization of the site of block are not dependable. The conduction time from the atrium to the BH (A-H time) was measured in the 18 patients with CHB distal to the BH and was within the normal range. With atrial pacing there was progressive lengthening of the A-H time, and Wenckebach phenomena were demonstrated in some cases. The conduction time from the His bundle to the ventricles (H-V time) in patients with block proximal to the His bundle was also within the normal range. Bilateral bundle-branch block was probably the mechanism of block in the majority of the patients with CHB; this emphasizes the clinical significance of ECG patterns indicating bilateral bundle-branch block during normal sinus rhythm with 1:1 A-V conduction.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Chordae tendineae from 50 normal mitral valves were studied. Four main types can be distinguished by their mode of insertion. Commissural chordae insert into and define the commissures between the anterior and posterior leaflets. Rough zone chordae insert into the ventricular aspect of the distal rough portion of the anterior and posterior leaflets. Such rough zone chordae typically split into three cords before inserting into the leaflet. Two of the anterior leaflet rough zone chordae are thicker than the others and are called strut chordae. They insert at 4 and 8 o'clock positions on the semicircular anterior leaflet. Cleft chordae insert into and define the clefts between the scallops of the posterior leaflet. Basal chordae are single strands that arise from the posterior ventricular wall and insert into the basal zone of the posterior leaflet. This classification permits a clear definition of mitral valve anatomy and forms a sound basis for functional studies of chordae tendineae.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Fifty normal mitral valves from adults were studied. Commissures, identified by commissural chordae tendineae and the tips of papillary muscles, partition the mitral valvular tissue into anterior and posterior leaflets. This definition incorporates into the posterior leaflet the structures formerly regarded as accessory leaflets. The posterior leaflet is further divided into scallops by clefts in its tissue. Cleft chordae provide a guide to these interscallop indentations or clefts. Partitioned this way, the posterior leaflet was tri-scalloped in 46 hearts. In 42, a large middle scallop was present with two smaller scallops on either side. Rough and clear zones can be defined on the anterior leaflet and rough, clear, and basal zones on the posterior leaflet.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Until the past decade, the diagnosis of congenital absence of the pericardium, partial or complete, had rarely been made prior to postmortem examination or thoracotomy.Since 1963, the condition has been recognized during life in six patients at this institution. Of these six patients, two had partial absence of the left pericardium and four had complete absence of the left pericardium. Characteristic roentgenologic findings were present in all six patients. Associated heart lesions were not present in either patient with a partial pericardial defect. Two of the remaining four had associated heart lesions. One patient had surgical repair of an atrial septal defect. Surgical repair of the pericardial defect was not attempted in any of the six patients. Hemodynamic determinations at rest were normal in all six patients. The two patients with partial pericardial defects, however, had elevation of the pulmonary artery and left ventricular end-diastolic pressures during mild exercise in the recumbent position which suggests that this type of defect is not totally innocuous. In view of the unusual and extreme cardiac mobility in this condition, it is conceivable that a portion of the heart could herniate and transiently incarcerate through the partial defect during exercise. It is suggested that partial pericardial defects may warrant surgical repair. Small defects or complete absence of the left pericardium, however, are apparently without lethal potential and do not require surgical intervention.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Three cases of intermittent obstruction of the mitral prosthesis (Cutter-Smeloff) due to ball variance have been reported. The typical findings were marked variation in the arterial pulse and the intensity of the mitral closing sound and intermittent absence of the opening click. The phonocardiography revealed varying intervals from aortic closing sound to the opening click (A2- OC interval). Hemodynamic studies revealed fluctuating aortic and pulmonary artery wedge pressures in spite of normal sinus rhythm, due to impaction of the ball into the prosthetic ring, opening only with severe elevation of the left atrial pressure. At operation, the balls showed yellowish discoloration, but no disruption of sutures nor thrombosis of the prosthesis was found. The incidence of this phenomenon was 9% with the Cutter-Smeloff mitral prosthesis, but no such case was seen among patients with the Starr-Edwards mitral prosthesis.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID